Buckle for a bag



FIG. 1 is a front elevation view of a buckle for a bag showing my new design;

FIG. 2 is a right side elevation view, with the left side elevation view being a mirror image thereof;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom plan view.

The broken lines are provided for illustrative purposes only and form no part of the claimed design. In addition, the portions of the buckle for bag that are not shown in the drawings, if any, do not form any part of the claimed design. 

The ornamental design for a buckle for a bag, as shown and described. 